This paper reports on the development of a simulation-based Design Assist Tool capable of assessing the circadian performance of architectural daylighting strategies during the design process. The tool integrates GIS site data, parametric modeling of multi-level building forms and multi-spectral lighting simulation of biological lighting effects into a Climate Based Daylight Modelling (CBDM) workflow capable of automatically performing hourly (or sub-hourly) time-series evaluations over selected days throughout the year. Outputs of the tool can be used to visually and quantitatively assess the extent to which a prospective daylighting design complies with emerging circadian lighting requirements over an annual period using daylight. An example application of the Design Assist Tool is presented to differentiate performance of varying building forms located on an urban site in Downtown Los Angeles.